Swell

Swell is the wave motion caused by a meteorological disturbance, which persists after the disturbance has died down or moved away. Swell often travels for considerable distances out of its generating area, maintaining a constant direction as long as it keeps in deep water. As the swell travels away from its generating area, its height decreases, though its length and speed remain constant, giving rise to the long low regular undulations so characteristic of swell. Two or three swells from different generating areas are often present and these may be partially obscured by the waves also present.